Examples of the diene rubbers include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), nitrile rubber (NBR) and hydrogenated nitrile rubber. Of the diene rubbers, the natural rubber (NR), the isoprene rubber (IR), the styrene-butadiene rubber (SBR) and the butadiene rubber (BR) have excellent processability and strength, so that they are widely used for tires, automobile parts and common industrial parts. The diene rubbers, however, have poor weathering resistance and ozone resistance, and therefore their products have a problem of short lifetime.
U.S. Pat. No. 4,645,793 discloses, as a diene rubber improved in the above properties, a blend of a diene rubber and an ethylene/.alpha.-olefin copolymer rubber. Though the blend is improved in the weathering resistance and the ozone resistance, it still has problems of insufficient strength properties, such as lower dynamic fatigue resistance (flexural fatigue resistance), lower vibration damping properties, lower vibration insulation properties, and lower adhesion strength to fibers than diene rubbers.
Japanese Patent Laid-Open Publication No. 143712/1996 describes an elastomer composition obtained by crosslinking a mixture of an ethylene/.alpha.-olefin/aromatic vinyl compound/nonconjugated diene copolymer and an elastomer. It is also described that this composition is excellent in mechanical properties such as tensile strength and abrasion resistance. However, the composition is not always sufficient in vulcanizing rate, strength properties and adhesion strength to fibers.
Of the diene rubbers mentioned above, the nitrile rubber and the hydrogenated nitrile rubber have excellent strength and oil resistance, and therefore they are widely used for sealing materials, rolls and belts. The nitrile rubber and the hydrogenated nitrile rubber, however, are poor in weathering resistance, ozone resistance, low-temperature properties and dynamic fatigue resistance, so that the lifetime of their products is short.
In "Japanese Rubber Association Bulletin 49, 236, 241, 246" (1976), a blend containing an ethylene/.alpha.-olefin copolymer rubber, which has been improved in the weathering resistance and the ozone resistance, is disclosed. Though the blend is improved in the weathering resistance and the ozone resistance, it still has problems of low dynamic fatigue resistance and low adhesion strength to fibers.
Because of excellent strength properties, heat resistance and weathering resistance, ethylene/.alpha.-olefin/polyene copolymer rubbers such as an ethylene propylene/diene copolymer are widely used for automobile parts, industrial rubber parts, electrical insulating materials, and civil engineering and building materials.
The ethylene/.alpha.-olefin/polyene copolymer rubbers, however, are poor in vibration damping properties, vibration insulation properties and dynamic fatigue resistance (flexural fatigue resistance), and therefore they have a problem of short lifetime when used for specified purposes such as rubber vibration insulators, rubber rolls, belts and tires.
Accordingly, there have been desired (1) elastomer compositions excellent in vibration damping properties, vibration insulation properties and strength properties as well as in heat resistance, weathering resistance, ozone resistance and dynamic fatigue resistance, (2) vulcanizable rubber compositions capable of producing vulcanized products not only having excellent strength properties, oil resistance, weathering resistance, ozone resistance, low-temperature properties and dynamic fatigue resistance but also having excellent adhesion to fibers when used for belts, and (3) elastomer compositions excellent in strength properties, vibration damping properties and vibration insulation properties as well as in heat resistance, weathering resistance and dynamic fatigue resistance (flexural fatigue resistance).
The present inventors have earnestly studied to obtain elastomer compositions having the above properties, and as a result, they have found that vulcanized products having the above properties can be obtained from compositions comprising an unsaturated olefin copolymer obtained by random copolymerizing ethylene, an .alpha.-olefin of 3 to 20 carbon atoms, a conjugated diene monomer, and optionally, an aromatic vinyl compound, and NR, SBR, NBR, hydrogenated NBR or EPT. Based on the finding, the present invention has been accomplished.